Pediatric patients with HIV infection and other immunosuppressive disorders are susceptible to Pneumocystis carinii pneumonia. Bronchoscopy with bronchoalveolar lavage may be technically more difficult to perform in pediatric patients. Because of this, an alterative diagnostic method which was safe and reliable had to be determined. Based on our adult data in which sputum induction has been shown to be a safe and highly sensitive procedure, we have undertaken a prospective assessment of the utility of sputum induction for the diagnosis of P. carinii pneumonia in children. A similar ultrasonic nebulization technique using hypertonic sodium chloride with either expectoration, oropharyngeal or nasopharyngeal suctioning has been employed. Data indicate that P. carinii can be reliably diagnosed by this technique in children as young as one year. The technique is a very safe and effective alternative to bronchoscopy for children. Initial data from this study have appeared in the Journal of Pediatrics. The project is ongoing, and a major goal is to further improve the sampling technique in order to increase sensitivity.